1. Field of the Invention
The present invention relates to the field of distributed computing, and more particularly to Web services.
2. Description of the Related Art
Web services represent the leading edge of distributed computing and are viewed as the foundation for developing a truly universal model for supporting the rapid development of component based applications over the World Wide Web. Web services are known in the art to include a stack of emerging standards that describe a service oriented, component based application architecture. Specifically, Web services are loosely coupled, reusable software components that semantically encapsulate discrete functionality and are distributed and programmatically accessible over standard Internet protocols.
Conceptually, Web services represent a model in which discrete tasks within processes are distributed widely throughout a value net. Notably, many industry experts consider the service oriented Web services initiative to be the next evolutionary phase of the Internet. Typically, Web services can be defined by an interface such as the Web services definition language (WSDL), and can be implemented according to the interface, though the implementation details matter little so long as the implementation conforms to the Web services interface. Once a Web service has been implemented according to a corresponding interface, the implementation can be registered with a Web services registry, such as Universal Description, Discover and Integration (UDDI), as is well known in the art. Upon registration, the Web service can be accessed by a service requestor through the use of any supporting messaging protocol, including for example, the simple object access protocol (SOAP).
Generally, in a distributed environment, the vast majority of Web services process requests indiscriminately. That is, regardless of the end-user, each request can be processed with equal priority. Given the exponential increase in requests for Web services across the Internet, however, some Web services provide for varying levels of responsiveness based upon what has been referred to as a “policy based service differentiation model”. In a policy based service differentiation model, Web services can offer many levels of responsiveness and performance depending upon administratively defined policies. In that regard, quality of service (QoS) terms in a service level agreement (SLA) specify a level of responsiveness minimally owed to particular requestors.
As Web services have grown from a novel technical concept to an accepted method for advertising and accessing distributed logic, application builders and developers have begun to compose applications as aggregations of Web services. To date, Web services have offered Quality of Service (QoS) guarantees for respective individual functions, but the problem of overall application QoS when using Web services in an application has fallen outside of scope.